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Astron. Astrophys. 328, 419-425

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Is SiS2 the carrier of the unidentified 21 micron emission feature?

G.F. Kraus1, J.A. Nuth III2, and R.N. Nelson3

1Physical Science Department, Charles County Community College, LaPlata, MD 20646, USA
2Astrochemistry Branch, Code 691, NASA/GSFC, Greenbelt, MD 20771, USA
3Chemistry Department, Georgia Southern University, Statesboro, GA 30460, USA

Received 23 February 1997 / Accepted 4 March 1997


Spectra are presented of SiS2 samples in a variety of crystal forms taken at both room temperature and at 600 K over the wavelength range from 5-25 microns. All spectra show strong features at 22.5 and 9.5 microns as well as less intense bands at 7.5, 8.5, and 12.5 microns. All room temperature spectra also show a feature at 10.7 microns that disappears on heating. One form of SiS2 shows strong correlated absorption features at 20 and 17 microns that are rapidly quenched by exposure to humid air with no significant change to the 7-13 and 22 micron features also present in the sample. These SiS2 spectra are consistent with previous spectra obtained by Nuth et al. (1985), are marginally consistent with the identification of SiS2 as the source of the observed 21 micron peak in several carbon-rich stellar sources, and suggest additional observations of these stellar sources that might confirm or refute the presence of SiS2. Specifically, if no feature at 17 microns is detected in objects that display the strong 21 micron emission feature then SiS2 should be ruled out as a candidate for this band.

Key words: line: identifications - stars: circumstellar matter - ISM: dust - infrared: lines and bands - methods: laboratory

Send offprint requests to: J.A. Nuth III

© European Southern Observatory (ESO) 1997

Online publication: October 30, 1997
Last change: March 24, 1998